In general, when operating a wind power generator, a wind velocity and a wind direction become a very important index for general controls and stability security of the wind power generator and thus the wind direction and the wind velocity are continuously measured using an anemometer.
FIG. 1 illustrates an installed state of general wind power generators and a met tower. Referring to FIG. 1, at a periphery of an installed location of wind power generators 100, a meteorological tower (met tower) is installed to measure an atmospheric state for operation of the wind power generator.
A met tower 10 includes an anemometer 11 and measures a standard wind velocity and wind direction in a wind farm in which the wind power generators 100 are installed. In this case, the measured wind velocity is used for measuring a standard wind velocity when displaying a power curve according to operation of the wind power generator 100.
FIG. 2 is a graph illustrating a power curve that is generated based on a generally measured standard wind velocity.
Referring to FIG. 2, in a power curve that is displayed by a standard wind velocity that is measured at the met tower 10, an x-axis represents a wind velocity and a y-axis represents generation power. In this case, a power curve is a most important index representing a performance of the wind power generator 100 and may be referred to as an output curved line and a performance curved line.
The wind power generator 100 is formed with a rotor blade 101, a hub 102, a nacelle 103, and a tower 104, and in this case, in an upper portion of the nacelle 103, a nacelle anemometer 110 is installed to measure a wind velocity (hereinafter, referred to as a ‘nacelle wind velocity’) at a location at which the wind power generator 100 is installed.
Such a nacelle wind velocity becomes a reference of a cut-in speed and a cut-out speed for driving the individual wind power generator 100.
FIG. 3 is a graph illustrating setting of a cut-in speed and a cut-out speed of a general wind power generator.
FIG. 3 illustrates a power curve of a general wind power generator 100. In FIG. 3, a cut-in speed represents a cut-in speed in which a generator actually starts to operate, and a cut-out speed represents a cut-out speed that stops a generator.
Here, because a cut-in speed is a wind velocity that starts to generate power by actually operating a generator, a low cut-in speed is good, but when the generator is operated in a very low wind velocity, generated power may be less than power in which a turbine consumes and thus the cut-in speed is generally about 3.5 m/s.
However, a cut-out speed is a wind velocity that artificially stops the wind power generator 100 in order to protect the wind power generator 100 when a wind velocity very largely increases, and each generator may set a different cut-in speed, but in order to secure stability, in a wind velocity of about 25 m/s, operation of the generator is stopped.
In this way, a cut-in speed and a cut-out speed of the wind power generator 100 is not set based on a standard wind velocity of the met tower 10 but is set based on a nacelle wind velocity that is installed in the wind power generator 100. This is because the met tower 10 is to measure a standard wind velocity and wind direction of a wind farm in which the wind power generator 100 is installed and the met tower 10 does not represent a wind velocity of the individual wind power generator 100.
Here, a nacelle wind velocity may sometimes become a reference of a power curve as well as a cut-in speed and a cut-out speed. Because the met tower 10 may not be installed in a wind force power generation region or wind velocities may be different according to an installation position/topography, a power curve may be measured using a nacelle wind velocity of each wind power generator 100.
However, a nacelle wind velocity that is measured in the nacelle anemometer 110 of the wind power generator 100 has a drawback representing a value different from a standard wind velocity that is measured in the general met tower 10 by an influence of a rotation of the rotor blade 101, a shape of the nacelle 103, and a momentary side wind of a periphery of a generator. That is, the nacelle anemometer 110 has a drawback that measures an inaccurate value when measuring a nacelle wind velocity due to an influence of an external environment like operation of the rotor blade 101 and a structure of the nacelle 103.
FIGS. 4 and 5 are graphs illustrating a relationship of a conventional met tower anemometer and a nacelle anemometer.
Referring to FIG. 4, when the rotor blade 101 of the wind power generator 100 rotates, a nacelle wind velocity that is measured in the nacelle anemometer 110 represents a value higher than a standard wind velocity of the met tower 10, as shown in a line A of FIG. 4. However, when the rotor blade 101 of the wind power generator 100 stops, a nacelle wind velocity that is measured in the nacelle anemometer 110 represents a value smaller than a standard wind velocity of the met tower 10, as shown in a line B of FIG. 4.
In such a situation, when the rotor blade 101 rotates, i.e., when the wind power generator 100 generates power, a nacelle wind velocity is larger than a standard wind velocity of the met tower 10 and thus when a power curve of the wind power generator 100 is output using the nacelle wind velocity, the power curve is drawn smaller than a power curve b based on a standard wind velocity of the met tower 10, as shown in a curved line a of FIG. 5. Therefore, when calculating accurate electric energy of the wind power generator 100 by a power curve, there is a problem that shows a very inaccurate result.
Further, when obtaining a cut-in speed and a cut-out speed for driving the wind power generator 100 based on an inaccurate nacelle wind, there is a problem that causes performance damage of the wind power generator 100.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.